AQA GCSE Combined Science: Trilogy Biology Paper 2 (Foundation), 2020: Question 6
9 marks · Standard Demand difficulty · Short Answer
This question covers DNA structure, the definition of a gene and genome, the application of genomic knowledge, and the concept of variation and natural selection in a population of snails.
Practise this questionQuestion
Question text
06 This question is about DNA and genes.
06.1 Which diagram represents a DNA molecule?
[1 mark]
Tick ( ) one box.
06.2 Describe the structure of a DNA molecule.
[1 mark]
06.3 A gene is a small section of DNA on a chromosome.
Complete the sentences.
[2 marks]
A gene codes for a particular sequence of .
This sequence makes a specific .
06.4 What is meant by the term genome?
[1 mark]
06.5 The complete human genome is now known.
Which important scientific advance was made using knowledge of the
human genome?
*20* [1 mark]
Tick ( ) one box.
Discovering antibiotic resistant bacteria
Finding more foods to eat from tropical forests
Tracing how aboriginal people spread across Australia
Working out when the last ice age ended22
A student found six different snails of one species in his garden.
Figure 7 shows the snails.
Figure 7
06.6 All the snails are different.
What scientific term describes differences in characteristics between individuals of
a species?
[1 mark]
06.7 A change in DNA has caused snail P to be very different from the other five snails.
Suggest why there might be an increasing number of snails similar to snail P in each
future generation.
[2 marks]
Mark scheme
Show the mark scheme
AO /
Question Answers Extra information Mark
Spec. Ref.
06.1 1 AO2
4.6.1.3
06.2 any one from: 1 AO1
• 2 strands / chains that are allow cross links between 2 4.6.1.3
twisted / coiled / spiralled strands / chains
• double helix
• (long) polymer
allow reference to nucleotides or
sugars, phosphates and bases
06.3 in this order only AO1
amino acids 1 4.6.1.3
protein allow polypeptide 1
06.4 all the genetic material (of an allow DNA / genes for genetic 1 AO1
organism) material 4.6.1.3
ignore chromosomes
06.5 tracing how aboriginal people 1 AO2
spread across Australia 4.6.1.3
06.6 variation ignore genetic/environmental 1 AO1
4.6.2.1
06.7 stronger / larger (shell) 1 AO2
4.6.2.2
(so) more likely to (survive and) 1
breed
or
(so) more likely to (survive and)
pass on genes
OR
(better) camouflaged (1)
(so) less likely to be eaten and
will breed more (1)
Total 9
How to answer it
DNA, Genes, and Evolution
This question assesses your recall of DNA structure, the definition of a genome, and your ability to apply the principles of natural selection and variation to a biological scenario.
06.1 & 06.2: Structure of DNA
✅ Correct Answer
The middle diagram (the double helix) represents DNA.
💡 Key Knowledge
DNA is a double helix. It consists of two strands that are twisted around each other. It is a long polymer made of repeating units called nucleotides.
06.3: Genes and Proteins
💡 Key Knowledge
A gene is a small section of DNA. It acts as a set of instructions:
- A gene codes for a particular sequence of amino acids.
- This sequence makes a specific protein (or polypeptide).
06.4 & 06.5: The Genome
💡 Key Knowledge
Genome: The entire genetic material of an organism.
🧠 Exam Technique
For 06.5, the correct answer is "Tracing how aboriginal people spread across Australia." This is an application of human genome mapping, which allows scientists to track migration patterns through genetic markers.
06.6: Variation
✅ Correct Answer
The term for differences between individuals of the same species is variation.
06.7: Natural Selection
📐 How to score 2 marks
To explain why snail P becomes more common, you must link the advantage to reproduction:
- The Advantage: State that the snail has a beneficial characteristic (e.g., a stronger/larger shell or better camouflage).
- The Consequence: Explain that because of this, it is more likely to survive and breed (or pass on its genes to the next generation).
❌ Common Errors
Students often forget the second part of the process. Simply saying "it is stronger" is not enough. You must explicitly state that survival leads to breeding and passing on genes to the next generation.
Topics
Biology · B6: Inheritance, Variation and Evolution
Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Biology Paper 2 (Foundation), 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.